Electromagnetic fuel injection control system for internal combustion engines

ABSTRACT

An electromagnetic fuel injection control system for an internal combustion engine, including a first monostable circuit having timing elements for receiving pulses relating to the speed of rotation of the engine, a second monostable circuit whose output is used to energize an electromagnetic fuel injection valve, and a charging-discharging circuit providing an output for use in varying the width of pulses in the first monostable circuit. The output of the first monostable circuit is applied as an input the second monostable circuit and is diverted for application as an input to the charging-discharging circuit.

ited States Patent Inoue et al. Mar. 7, 1972 54] ELECTROMAGNETIC FUEL 1 Retereneee Cited INJECTION CONTROL SYSTEM FOR UNITED STATES PATENTS INTERNAL COMBUSTION ENGINES 3,338,221 8/1967 Scholl ..123/32 EA inventors: Talmhl luoue; Yoshllkl Abe, both of l-ligashi-Matsuyama, Japan Assignee: Diesel Klld Kabushlkl Kalsha, Tokyo,

Japan Filed: Mar. 24, 1970 Appl. No.: 22,154

Foreign Application Priority Data Mar. 24, 1969 Japan ..44/31255' U.S.CIL ..l23/32E, 123/119, 123/139 E Int. (I ..F02d 5/00 Field ofSearch ..123/32 AE, 32 EA, 119, 139

3,483,851 12/1969 Reichardt..... 3,521,606 7/1970 Schmidt Primary Examiner-Laurence M. Goodridge Attorney-Otto John Munz [57] ABSTRACT An electromagnetic fuel injection control system for an internal combustion engine, including a first monostable circuit ,having timing elements for receiving pulses relating to the ;speed of rotation of the engine, a second monostablc circuit ;whose output is used to energize an electromagnetic fuel ini jection valve, and a charging-discharging circuit providing an output for use in varying the width of pulses in the first monostable circuit. The output of the first monostable circuit 'is applied as an input the second monostable circuit and is diverted for application as an input to the charging-discharg- --ing circuit.

1 Claims, 3 Drawing Figures PAIENTED MR 7 I972 SHEET 2 [IF 3 INVENTORS TAKASHI INOUE, YOSHIAKI ABE y My ATTORNE PATENTEDHAR 1 \912 3. 646. 9 1 6 SHEEI 3 0r 3 FIG.3

I NVENTOR TAKASHI INOUE, YOSHIAKI ABE ATTORNEY ELECTROMAGNETIC FUEL INJECTION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES The present invention relates to an electromagnetic fuel injection control system for internal combustion engines for automobiles.

Internal combustion engines in automobiles nowadays are required to develop high torque output even under general high-speed running conditions, to run with a minimum of fuel consumption for engine speeds particularly up to an intermediate level and to burn the fuel effectively for clean exhaust gases.

In conventional electromagnetic fuel injection control systems, the rate of change I (the duration of energization of the magnetic injection valves) over the engine rpm. range from idling level a to maximum output torque level 11, as shown in FIG. 1 (which is a graph showing r.p.m. characteristic of fuel requirement), must be constant for all values of intake-pipe negative pressure. What is meant by this constancy will be explained by referring to FIg. 1, wherein t, stands for pulse width corresponding to the energizing duration, and is taken for the vertical axis, while the horizontal axis represents the engine r.p.m. N. P stands for intake-pipe negative pressure taken as the parameter. The variation of pulse width 1 is represented by At.

By constancy mentioned above is meant that, for the three values of negative pressures P,, P, and P for example, the respective ratios of At,, At A1 to maximum energizing durations 1,, t and 1 are equal:

At,/t, Ae/r A2,]: K (constant).

FIG. 1 is a graph showing r.p.m. characteristics of the fuel requirement of an engine.

FIG. 2 is a circuit diagram of an electromagnetic fuel injection system having a compensating circuit according to the present invention.

FIG. 3 is a diagram illustrating voltage waveforms occuring at various points in the circuit of FIG. 2.

The present invention modifies the above mode of change to introduce a secondary characteristic for satisfying the requirements imposed on internal combustion engines under consideration.

According to this invention, an electromagnetic fuel injection control system is able to provide a high output torque by fully supplying a fuel to an engine at its revolving speed above the point b shown in FIG. 1 (for example above 4,000 r.p.m.) and to match the amount of fuel supplied to the engine requirements to obtain desired performances for fuel consumption, quality of exhaust gases and idling running etc., in response to changes in an intake-pipe pressure P at the revolving speed of the engine below the point b.

In the example shown in FIG. 2, which is a circuit diagram of an electromagnetic fuel injection system having a compensating circuit according to this invention, sections A, B and C consist of known circuits and apply energizing pulses to electromagnetic fuel injection valve 38. The first section A is a monostable multivibrator composed of a pulse-generating circuit having a 2-lobe cam 1 and a breaker point 2 and having transistors 16, 23 and transformer T. The second section B is another monostable multivibrator having transistors 24, 31, 33. The third section C is an output amplifier having a transistor 37 and injection valve 38 of which electromagnetic coil L is a part.

The operation of section A starts with the on-off action of breaker point 2 actuated by earn 1, which is driven from the engine. As point 2 so operates, a rectangular pulse waveform, represented by waveform U in FIG. 3 (which illustrates voltage waveforms occurring at various points of the circuit in FIG. 2), occurs at connection point U, shown in FIG. 3. Next, waveform U is differentiated by the differential-action elements, comprising condenser 4 and resistor 7, thereby delivery positive and negative trigger pulses to a connecting point 6. Diode 8 passes the negative trigger pulses from point 6 forward to connection point U,. The negative trigger pulses are indicated by waveform U, in FIG. 3. As a negative trigger pulse arrives at point U,, transistor 16 becomes nonconductive and, consequently, transistor 23 becomes conductive. With transistor 23 conducting, current flows in primary winding 20 of transformer T and increases exponentially according to the time constant determined by the inductance of winding 20 and resistor 22 until it reaches the maximum value determined by the resistance values of winding 20 and resistor 22. During this increase, an exponentially decreasing voltage is induced in secondary winding 19 to maintain the base of transistor 16 at negative potential. When the induced voltage has fallen, the base of transistor 16 becomes positive in potential to cause this transistor to conduct and, consequently, transistor 23 becomes nonconductive, thereby completing one cycle of operation. The interval from the moment the base of transistor 16 becomes negative to the moment the same base becomes positive corresponds to pulse width T, in waveform U shown in FIG. 3. This width is dependent upon the dividing ratio of the voltage divider consisting of resistors 11 and 9 and also on the inductance of primary winding 20. The core 21 of transformer T is adapted to assume a position corresponding to the pressure in the engine intake pipe, so that the output pulse width T, from this monostable multivibrator is related to said dividing ratio and intake-pipe negative pressure. Since point U is connected to the base of transistor 37 through resistor 36, the output pulses reach the base of transistor 37. For arrival of each pulse with width T,, transistor 37 conducts for the duration of the pulse width T, to keep injection valve 38 open for that duration.

The base of transistor 24 in section B is at positive potential for the duration of positive pulse width T, of the pulse U This potential is at a halfway level, approximately, between negative supply conductor 86 and positive supply conductor 87. When this transistor 24 conducts for the duration of positive pulse width T, of the pulse U its collector current flows into condenser 26 and charges this condenser 26 linearly. While the charging is in progress, the voltage across the condenser 26 rises linearly. This is represented by the waveform U, in FIG. 3. When the positive pulse of width T, disappears and the transistor 16 becomes again conductive, the base of transistor 24 turns considerably negative with respect to positive conductor 87 and, consequently, this transistor stops conducting. Then, condenser 26 begins to discharge through resistor 32, and transistors 31, 24, and 16. The falling voltage of the condenser due to this discharging is represented by the sawtooth in waveform U, in FIG. 3. While this discharging is in progress, point U is negative, so that diode 30 keeps the base of transistor 33 at negative potential and holds this transistor in nonconductive state until condenser 26 becomes fully discharged. Then, during the discharging of the condenser 26, a positive pulse is induced at the point U to which the collector of transistor 33 is connected. By means of the positive pulse of waveform U the base of transistor 37 through the resistor 35 stays positive to make this transistor 37 conduct for the duration of width T to energize the coil L of valve 38. Now, it will be recalled that the base of transistor 37 is connected to point U, in section A so that valve 38 is kept open also during pulse width T,. Since width T,, immediately follows width T,, the valve is kept open continuously from the beginning of width T, to the end of width T,. Assuming that the total duration is represented by T,,, the interval of the total duration T,, is the sum of the pulse width T, of the pulse U and the pulse width T, on the point U in the monostable circuit B, that is, T, T, T, as shown by waveform U in FIG. 3. Since the charging voltage of the condenser 26 is proportional to the pulse width T,, its charging time is also proportional to the pulse width T,, and consequently, by producing at the connection point U pulse width T having the pressure in intake pipe as a parameter, a compensating effect which is described hereinafter is readily obtained.

In the compensating circuits D and E according to this invention, shown in FIG. 2, transistor 45 has its base connected to negative supply conductor 86 through resistor 42 and also to the cathode of diode 43, whose anode is connected to positive supply conductor 87 through resistor 44 and also to the collector of transistor 16 through condenser 41 and resistor 40 connected in series. The emitter of this transistor 45 is connected to negative conductor 86, and the collector to positive conductor 87 through connection point U, and resistor 46. The base of transistor 49 is connected to negative conductor 86 through resistor 47 and also to connection point U, through resistor 48; the emitter direct to negative conductor 86; and the collector to positive conductor 87 through connection pint U and resistor 50. The base of transistor 53 is connected to the collector (point U of transistor 33 through resistor 51 and also to the collector (point U of transistor 49 through resistor 52; the emitter direct to negative conductor 86; and the collector to positive conductor 87 through point U and resistor 54. The base of transistor 57 is connected to negative conductor 86 through resistor 55 and also to the collector (point U of transistor 53 through resistor 56; the emitter direct to negative conductor 86; and the collector to positive conductor 87 through connection point U and resistor 58 and also to the cathode of diode 66 through resistor 65. The base of transistor 61 is connected to the collector (point U,,) of transistor 53 through resistor 59 and also to the collector (point U,;) of transistor 49 through resistor 60; the emitter direct to negative conductor 86; and the collector to positive conductor 87 through point U and resistor 62 and also to the anode of diode 66 through diode 63. Between connection point U through which diode 63 is connected to diode 66, and negative conductor 86 is provided condenser 64. The base of the transistor 68 is connected to the anode (point U of diode 66; the emitter to negative conductor 86 through resistor 67; and the collector direct to positive conductor 87. By the foregoing circuit elements and connections, a charging-discharging network is formed to constitute section D. The base of transistor 74 is connected to negative conductor 86 through resistor 71 and also to the cathode of diode 72, whose anode is connected to the collector (point U of transistor 16 through series-connected condenser 70 and resistor 69 and also to positive conductor 87 through resistor 73; the emitter direct to negative conductor 86; and the collector to positive conductor 87 through connection point U and resistor 75. The base of transistor 78 is connected to negative conductor 86 through resistor 77 and also to the collector (connection point U of the transistor 74 through the resistor 77; the emitter direct to negative conductor 86; and the collector to positive conductor through point U and resistor 79 and also to the cathode of diode 80. The base of transistor 83 is connected to negative conductor 86 through point U and condenser 81, to the anode of diode 80 and to the emitter of transistor 68 through resistor 82; the emitter to the secondary winding 19 of transformer T through resistor 84 and connection point 85; and the collector to positive conductor 87. The circuits involving these transistors 74, 78 and 83 constitute another charging-discharging network forming section E.

The sections D and E, formed as above, operate in conjunction with monostable multivibrators A and B in the following manner: condenser 41 is charged through resistor 40 with the positive pulse of waveform U FIG. 3. For the duration of this pulse whose width is T transistor 45 stays off. As the potential of point U falls upon lapse of width T,, condenser 41 discharges through resistors 40, 44 and keeps transistor 45 in nonconductive state until it becomes fully discharged. During this discharging, diode 43 does not conduct and thereby keeps the base of transistor 45 at negative potential. The duration of this nonconductive state is roughly determined by the ohmic size of resistors 40 and 44 and condenser 41. During this nonconductive state, the collector of the transistor 45 is supplied with positive voltage T shown as U, in FIG. 3, whose positive pulse with width T corresponds to the nonconductive duration. Note that width T follows width T immediately. The variation of the collector voltage of the transistor 45 is transmitted to the base of transistor 49 through divider resistors 47, 48, so that potentially inverted pulse form U shown as U in FIG. 3 appears on the collector of transistor 49. The inverted waveform, shown as U in FIG. 3, is applied through resistor 52 to the base of transistor 53, to which waveform U too is admitted through resistor 51 from section C. Transistor 53 is of NPN type so that it becomes nonconductive only when both wavefonns U and U are simultaneously at the potential of negative conductor, that is to say, for the duration of the width T.,. The transistor 53 develops a pulse of waveform U, on its collector. The pulse U is applied through resistor 56 to transistor 57 and is inverted by transistor 57 so that the inverted pulse appears at its collector which is shown as width T, of waveform U in FIG. 3. When the voltage across transistor 57 is negative during the period of width T',, the charge in condenser 64 dissipates.

Condenser 64 is charged as follows: since the base of transistor 61 receives two pulses, U through resistor 59 from transistor 53 and U from transistor 49 through resistor 60, the NPN-transistor 61 becomes nonconductive only when the two pulses are negative in polarity simultaneously, that is to say, for the duration of the width T The transistor 61 produces a pulse which is shown as pulse U in FIG. 3 at its collector. The pulse U with width T applies through diode 63 to point U located on the cathode side of diode 63, which conducts when the potential of pulse U is higher than the potential of point U and, by so conducting, charges condenser 64 instantly. For the duration of T, of the pulse U,,,, the condenser discharges through series-connected diode 66 and resistor 65 and also collector-emitter of transistor 57. Diode 66 becomes nonconductive when the transistor is nonconductive and the potential of its collector rises to equal that of positive conductor 87. Just when this equality is reached, condenser 64 stops discharging. The rise of the potential at point U is abrupt but its fall is gradual, presenting such a form as is represented by waveform U in FIG. 3. Thus, when the intake-pipe pressure falls, not shown, to decrease pulse width T, of the pulse generated by monostable circuit A, the as-charged voltage of condenser 26 decreases to bring back the tailing end of width T, of the positive pulse generated by the second monostable circuit B toward the dotted line shown in waveform U in FIG. 3. Since pulse width T;, of the pulse U remains unchanged, the charging time T for condenser 64 shortens while the discharging time T, increases. By this increase of discharging time, the potential of point U after the completion of the discharging, tends to approach the potential of negative conductor as shown by the dot line in waveform U Fig. 3. The time constant for discharging can be varied by changing the resistance of resistor 65 and the capacity of condenser 64. The potential of point U applies to the base of transistor 68, so that a pulse similar to that at point U appears at the collector of this transistor and applies to condenser 81 through resistor 82, whose resistance value is sized relatively large so as to provide a highly exponential charging characteristic by a large time constant. On the other hand, pulse waveform U whose pulse width is constant, is generated by a monostable multivibrator circuit consisting of condenser 70 and transistor 74. The pulse waveform U follows the positive pulse width T of pulse U as will be noted in FIG. 3, and applies to the base of transistor 78 to produce an inverted pulse from pulse U shown as U in FIG. 3, at the collector of transistor 78. Note that pulse U is identical to pulse U except for inverted polarity. Since the collector of transistor 78 is connected to point U through the cathode of diode 80, no charging current flows into condenser 81 during the period of T',;, which is the pulse width of pulse U and for which the potential of point U is at that of negative conductor. When pulse U is positive at point U condenser 81 becomes charged exponentially through resistor 82 and its voltage rises toward the potential of the emitter of transistor 68. The exponentially rising potential of point U due to this charging is represented by the pulse U in FIG. 3. The peak value of this pulse width T is determined by the after-discharge voltage of waveform U which varies with intake-pipe pressure and also by the pulse width T which varies with engine r.p.m. The conductivity of transistor 83 through its emitter and collector is varied by means of this variable pulse of waveform U As was stated previously, the pulse width T, can be varied by varying the potential of connection point 85 in section A. This means that, since the emitter of transistor 83 is connected to point 85 and acts as a variable conductance element paralleled to resistor 11, the pulse width T will vary as this conductance is varied. The variation of pulse width T affects pulse width T It follows therefore that the energizing pulse width T varies with engine r.p.m. and intake-pipe pressure. Stated specifically, if intake-pipe pressure is low, the as-charged voltage of condenser 81 will be low, as illustrated by the dot line in waveform U FIG. 3, and the resistance through the emitter and collector of transistor 83 is large. This variable resistance is little afiected by changes in engine r.p.m., so that the potential of point 85 is similarly little affected by changes in engine r.p.m. Consider engine r.p.m. to be rising from the low-speed range toward the high-speed range during operation, and suppose the engine rpm to rise past the point b" assumed to stand for 4,000 rpm At this speed of the engine, the charging duration and as-charged voltage (that is to say, voltage when as fully charged as ever in the cycle, or peak-charged) of the condenser 81 the condenser 81 become both nil to maximize the internal resistance of transistor 83 and thereby reduces the potential at point 85 to the minimum level. As engine r.p.m. continues to rise, the as-charged voltage remains nil. In other words, above 4,000 r.p.m., the condenser voltage stays zero.

Consider, next, a high intake-pipe pressure. In this case, the condenser voltage is high, as illustrated by the solid line in waveform U By virtue of the variable conductance of transistor 83, the high as-charged voltage of condenser 81 results in a high potential at point 85, and the variation of this potential with engine r.p.m. is extensive. For engine r.p.m. levels above 4,000 r.p.m., the as-charged voltage becomes zero as stated before. This manner of influencing the potential at point 85, it will be readily noted, satisfies the requirements represented by solid-line curves in FIG. 1. The modified secondary characteristic thus obtained can be altered at will by changing the setting of variable resistor 84 to change pulse width T Changing the setting of resistor 65 changes the discharge characteristic of condenser 64 to alter the gradient of All! curve, which is otherwise dependent solely on intakepipe negative pressure so that the desirable rates of change in valve energizing duration, that is, At,/t, At /t At /t can be secured. In the foregoing description, width T and width T of FIG. 3 were explained in the same manner so as to simplify the explanation. As to width T this width was explained as a voltage waveform exponentially rising while the condenser 64 is charged. If the condenser 64 is charged from point U in FIG. 2, with the positive pulse with width T which rises exponentially, a perfect square waveform may not result and such a poorly defined square wave may introduce a small time gap, if any, between the end of T, and the beginning of T at the time of producing pulse width T T, T Where the desired performance is such that a small time gap is of no consequence, then condenser 64 can be charged directly from connection point U thereby eliminating the circuit for generating pulse width T Since it is possible, according to this invention, to widely vary the rate of change of pulse length for revolving speed of the engine in response to changes in the intake-pipe pressure in internal-combustion engines, the injection quantity characteristic of the fuel injection can be readily made to match such fuel requirement characteristic as is shown in FIG. 1.

What is claimed is:

1. In an electromagnetic fuel injection control system for internal combustion engines having fuel injection valves which are energized on reception of first and second output pulses respectively from a first and a second monostable circuit, said first monostable circuit being arranged to receive trigger pulses related to the speed of rotation of the engine, said first out- Eut pulse having a variable ulse length, said second monostale circuit having its time 0 operation controlled by said first output pulses, the improvement comprising:

A. a third monostable circuit connected to receive the first output pulses from said first monostable circuit to generate third output pulses from the third monostable circuit,

B. a first capacitor charging and discharging circuit further comprising:

Bl. a logical circuit connected to receive said third output pulses and said second output pulses for logically combining the second and third output pulses to produce a waveform, and

B2. means responsive to said waveform for controlling the charging and discharging of a first capacitor, thereby producing an output voltage, and

C. a second capacitor charging and discharging circuit further comprising:

C]. a fourth monostable circuit for receiving said first output pulses for generating fourth output pulses, and

C2. means responsive to said fourth output pulses for controlling the charging and discharging of a second capacitor for generating a pulse signal which varies in length as a function of the fourth output pulses. 

1. In an electromagnetic fuel injection control system for internal combustion engines having fuel injection valves which are energized on reception of first and second output pulses respectively from a first and a second monostable circuit, said first monostable circuit being arranged to receive trigger pulses related to the speed of rotation of the engine, said first output pulse having a variable pulse length, said second monostable circuit having its time of operation controlled by said first output pulses, the improvement comprising: A. a third monostable circuit connected to receive the first output pulses from said first monostable circuit to generate third output pulses from the third monostable circuit, B. a first capacitor charging and discharging circuit further comprising: B1. a logical circuit connected to receive said third output pulses and said second output pulses for logically combining the second and third output pulses to produce a waveform, and B2. means responsive to said waveform for controlling the charging and discharging of a first capacitor, thereby producing an output voltage, and C. a second capacitor charging and discharging circuit further comprising: C1. a fourth monostable circuit for receiving said first output pulses for generating fourth output pulses, and C2. means responsive to said fourth output pulses for controlling the charging and discharging of a second capacitor for generating a pulse signal which varies in length as a function of the fourth output pulses. 